diff --git a/filters.go b/filters.go index afc4be8..4e6eeb3 100644 --- a/filters.go +++ b/filters.go @@ -170,12 +170,19 @@ func Bilinear(img image.Image, factor [2]float32) Filter { } func splineKernel(B, C float32) func(float32) float32 { + factorA := 2.0-1.5*B-C + factorB := -3.0+2.0*B+C + factorC := 1.0-1.0/3.0*B + factorD := -B/6.0-C + factorE := B+5.0*C + factorF := -2.0*B-8.0*C + factorG := 4.0/3.0*B + 4.0*C return func(x float32) (y float32) { absX := float32(math.Abs(float64(x))) if absX <= 1 { - y = (absX*absX*((12.0-9.0*B-6.0*C)*absX+(-18.0+12.0*B+6.0*C)) + (6.0 - 2.0*B)) / 6.0 + y = absX*absX*(factorA*absX+factorB) +factorC } else if absX <= 2 { - y = (absX*(absX*(absX*(-B-6.0*C)+(6.0*B+30.0*C))+(-12.0*B-48.0*C)) + (8.0*B + 24.0*C)) / 6.0 + y = absX*(absX*(absX*factorD+factorE)+factorF) + factorG } else { y = 0 }